In case of operating a power system, a power supplier who generates or distributes power makes a request for power adjustment (reduction or increase) of a customer who utilizes the power. By this request, technique to control power demand-supply balance (as balance between a power demand amount and a power supply amount) in all the power system is proposed.
Based on the power demand amount and the power supply amount previously estimated, the power supplier requests the power adjustment of each customer. In response to this request, the customer performs the power adjustment. Accordingly, a time lag occurs between a time when the power supplier requests the power adjustment and a time when the customer starts the power adjustment.
If accuracy of control of power demand-supply balance is prioritized, the time lag had better be shortened. However, it often happens that a time when the power supplier requests the power adjustment of the customer is just before a time for the customer to start the power adjustment. In this case, the customer might not perform the power adjustment. Otherwise, burden of the customer is more increased.